The agency, which has handled the account for eight years, retained the business in a final shoot-out against OMD.
Five agencies, including OMD, Carat, Starcom MediaVest, Dentsu Media and MEC, initially responded to the airline's tender. Starcom subsequently withdrew because of a conflict with its Emirates client.
SIA has been hit by the decline in passenger traffic in the past few months and has been cutting flights to the US, Europe and Asia.